1. Field of the Invention
The present invention has to do with improved compositions of benzoyl peroxide and methods of processing benzoyl peroxide. More particularly, the invention relates to the use of a composition such as TRANSCUTOL.RTM. diethylene glycol monoethyl ether as a processing aid for making a new benzoyl peroxide premixture which can be admixed with an aqueous medium to make a new benzoyl peroxide flocculent composition.
2. The Related Art
Benzoyl peroxide is most commonly employed as an active ingredient in topical compositions which are used in the treatment of acne and other dermatological conditions. Topically applied compositions used to treat the skin normally require that the benzoyl peroxide be ground to a fine particle size in a suitable vehicle before use. If the benzoyl peroxide is not ground, the product will be grainy and scratchy on the skin. Moreover, the clinical efficacy as related to the surface area of active ingredient on the skin, which in turn is a function of particle size, would be expected to be reduced for a given concentration of benzoyl peroxide when larger particles are employed. It is also known that benzoyl peroxide is a potentially explosive oxidizing agent and it must be ground under controlled conditions in a medium that prevents excessive heat build-up. Current manufacturing processes, therefore, are difficult, time consuming and potentially hazardous.
Benzoyl peroxide containing acne treatment compositions are disclosed in U.S. Pat. No. 4,606,913. The patent has to do with high internal phase emulsions and their use as suspending mediums for cosmetics and drugs. The emulsions are the water-in-oil type and, as an example, they can be used to make an acne cream comprised of water, mineral oil and benzoyl peroxide. The patent also discloses various cosmetic adjunct materials which can be used when the high internal phase emulsions are employed as a vehicle for cosmetic ingredients and these include solvents such as ethylene glycol monoethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether and several others. The compositions are prepared by adding the aqueous phase to the oil phase. Ingredients that are part of the aqueous phase are added into the aqueous phase before the phases are brought together.
Antiacne compositions combined with sun filters are disclosed in U.S. Pat. No. 4,671,956. The compositions are for the local treatment of acne and they contain from 0.5% to 20% by weight of benzoyl peroxide in association with at least one sun filter. The benzoyl peroxide is used in the form of a finely divided powder in the dry or moist state, preferably in the moist state. The antiacne compositions are in the form of emulsions and are prepared by adding benzoyl peroxide in the aqueous phase and the sun filter either in the aqueous phase or oil phase depending on its affinity. Propylene glycol is disclosed as an ingredient of the compositions as a humectant and solvents such as lower aliphatic alcohols can be incorporated in gel-type preparations.
According to U.S. Pat. No. 5,019,567, quaternary ammonium lipophilic salicylates are combined with benzoyl peroxide to prepare compositions for the treatment of dermatoses, acne, warts, skin dyskeratinization, cutaneous ulcers and other cutaneous disorders. The patent exemplifies gel compositions which include diethylene glycol monoethyl ether as an ingredient, among others, but there is no disclosure of the method of preparing the gel.
We have now discovered an improved method of processing benzoyl peroxide to make a premixture which can be admixed with an aqueous medium to make a new flocculent composition. The flocculent composition itself feels smooth or impalpable when rubbed on the skin. Our method is easier, faster and safer than conventional techniques which employ grinding to reduce the particle size of the benzoyl peroxide and the particles of benzoyl peroxide in our flocculent composition are substantially smaller than those which are obtained by conventional grinding.